The invention relates to a microvalve. More particularly it relates to a microvalve which has pressurized-medium connections and a valve seat inserted between them with which a closure member is associated and is deflectable by electrical actuating means.
GB 2,155,152 A has already disclosed such a microvalve which is produced in the multilayer structure known from semiconductor technology. This micromechanical valve has essentially three layers, of which an inlet and an outlet, and also a valve seat are constructed in a silicon base layer and an intermediate layer adjoins said base layer and also an outer covering layer adjoins the latter. The layers form a space producing the pressurised-medium link between the two connections. In this microvalve, the covering layer is at the same time constructed as a membrane into which a closure member belonging to the valve seat is integrated. When this microvalve is operated, an electrostatic actuating device disposed on the membrane has to overcome not only the forces of the resilient membrane but also the fluid pressure present in the inlet since the membrane which closes the valve seat is not compensated with respect to this pressure. The result of this is that the microvalve is suitable only for relatively low pressures and consequently produces a relatively low hydraulic switching power. The dynamic behaviour of the micromechanical valve is consequently also adversely affected. The non-pressure-compensated construction of the microvalve results, in addition, in relatively large actuating forces and consequently in relatively expensive actuating devices.
Reference is furthermore made to the publications EP 0,250,948 A2 and EP 0,261,972 A2 in which the technology of producing such microvalves is described more precisely and it is explained how three-dimensional shapes can be machined in multilayer structures so that different mechanical elements are possible as a result of combining different structural details. The microvalve can consequently be constructed as a 2- or 3-way valve. The membrane can also be disposed in an intermediate layer.